Abrasive article



Patented July 19, 1938 I UNITED STATES PATENT OFFICE ABBASIVE ARTICLE Robert P. Courtney, .Maplewood, N. 1., assignor to Bakelite Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application May 18, 1934, Serial No. 726,366

14 Claims. (Cl. 51-278) This inventionrelates to abrasive articles, such and the varnish will remain on or near the suras sandpaper and the like, and to a novel method face. It will usually dry on the sufface suffor the production of such articles, and is parficiently to prevent material penetration before ticularly directed to a method and product inthe non-solvent has evaporated from the fibrous volving an improved bonding medium for attachbase. The same varnish applied without emulsi- 5 ing abrasive grains to a fibrous base. fying in a non-solvent will penetrate the fibrous Varnishes composed of drying oils, raw or base quite readily. modified, with or without natural or synthetic A varnish of low viscosity, when made into an resins, or of resins alone, dissolved in suitable emulsion and applied to a fibrous base, will sursolvents have heretofore been used as adhesives round abrasive particles subsequently placed 10 for bonding sand, grits, or other abrasive parupon the wet surface more readily and fix them ticles to fibrous bases such as paper, cloth, and more strongly than the same varnish treated the like. to give a higher viscosity.

There are several disadvantages involved in Such emulsions of low viscosity varnishes are this procedure. If on drying or baking the more easily manufactured, keep better, and are 15 varnish or adhesive becomes brittle it is essential more easily applied to the fibrous base than the that it should not penetrate too deeply into the same varnish made to a higher viscosity. fibrous base, else it will cause the fibrous base and A substantial saving is effected in quantities the resulting abrasive article to be brittle and to used, due to lowered penetration. Moreover,

lack strength and shock resistance. Even if the such emulsions, if of the oil-in-water type, or, 2o dried varnish is flexible it is desirable that the more exactly, varnish in non-solvent, can be fibrous base should not be penetrated very deeply thinned with the non-solvent. Many non-solfor reasons of economy in the use of the binding vents, especially water, are cheaper than solmedium. vents for these materials.

To reduce such penetration, varnish composi- It is advantageous to control the conditions 25 tions of the type described above have been under which the emulsion of the varnish comheated or otherwise treated so as to very substanposition is made so as to favor the dispersion of tially increase their body or viscosity. As a rethe varnish in the water or other non-solvent. sult they are sometimes difficult to manufacture It is possible, however, to have the water in the due to the tendency of the varnish to become disperse phase in a varnish medium provided the 30 completely solid while bodying, before the heatconditions of use are such that when the emuling or other treatment can be discontinued. For sion is applied to a fibrous base the water parthe same reason the keeping quality of such ticles contact the base and there is a preferenvarnish compositions is often unsatisfactory. tial absorption of the water particles by the base.

Varnishes of such high viscosity are frequently As an illustration of a varnish emulsion suit- 35 more diflicult to handle in applying to the able for use in the present invention, an oil-resin fibrous base than a less viscous liquid. composition is prepared in accordance with the These viscous or heavy bodied varnish comdisclosure of U. S. Patent 1,677,417 to Turkington, positions have a decreased tendency to flow from cresol, formaldehyde, tung oil, and some around the abrasive particles. It is largely upon rosin with hexamethylenetetramine as a con- 40 this surrounding of the abrasive particle that the verting agent. A suitable solvent, such, for exstrength of adherence of the adhesive to the ample, as a mixture of xylol and butyl acetate is particle depends, so that the increasing of the added to form a varnish. An emulsifying agent, viscosity of the varnishes entails a very decided for example, triethanolamine is also preferably disadvantage in lessened bonding strength as added. In general, the amount of triethanol- 45 compared with the more fluent compositions. amine or other emulsifying agent added to the I have found that if varnishes of the type deoil-resin composition is advantageously about 2 scribed above, but having a relatively low viscosto 10% of the water used in forming the emulity, are emulsified in water or other non-solvent sion. The varnish thus prepared is then gradubefore applying to the fibrous base the following ally added to the water with agitation to form 50 advantages are obtained: an emulsion. Pigments, colors, or other addi- If the non-solvent has a preferential ability to tion agents can be incorporated with the comwet the fibrous backing, which is usually the case position at this stage, if desired. when water is used as a non-solvent medium, the The amount of varnish that can be included in backing will be first wetted by the non-solvent a given amount of water with the varnish re- 55 maining as the disperse phase depends upon the agent and speed of agitation; but as high as 99% of the emulsion can be varnish without changing over into a water-in-varnish emulsion as indicated by tests made by diluting with water.

As an additional illustration of a suitable composition, an oil-soluble resin is prepared by reacting a phenyl-phenol compound with formaldehyde, preferably with the amount of formaldehyde in excess of molecular proportions, in the presence of a catalyst such as oxalic acid. This resin after dehydration is made into a varnish by heating with a fatty oil, for example, as tung oil; best results seem to follow from heating about equal weights of resin and tung oil for about an hour at about 200 C. and then incorporating such additional amounts oi. tung oil or other fatty oil or mixture of tung oil and other fatty oil as linseed oil, as may be desired, followed by a short heating period. For air-drying varnishes or coating compositions it is desirable to include a small percentage of a drier such as 0.1 to 1.0 per cent of cobalt linoleate or other known drying agent. Suitable solvents suchas petroleum solvents, cellosolve (monoethyl ether of glycol), xylol or mixtures of these are stirred into the mass while it is maintained at a'suitable temperature; the amount of solvent added depends upon its insolubility in water and the viscosity desired, but a weight of a water insoluble solvent as specified above equal to the weight of the oilresin composition yields a varnish suitable for most purposes. To prepare an emulsion of such a varnish, casein, for example, is dispersed in water made ammoniacal by the addition of strong ammonia; the varnish is slowly added into the casein solution and agitation causes an emulsion to form. The more rapid the agitation the thicker will be the emulsion. If the varnish is added too rapidly, the emulsion may become one of water in varnish, but slow addition and rapid agitation produces a varnish in water emulsion. The nature of the emulsion is determined by adding a small amount to water; if it can be dispersed in the water it is regarded as one of varnish in water. Varnish in water emulsions are preferred since the possibility of dilution with water permits the use of relatively small amounts of water-insoluble solvents in the preparation of the varnishes.

As emulsifying agents a wide variety of substances can be used. For example, gelatin, camphor, tannic acid, lamp black, lead acetate, starch, gum arabic, acid casein solution, soaps and the like normally produce emulsions of varnish in water. Bentonite, ammonium linoleate, triethanolamine and its fatty acid soaps or compounds and basic casein solutions quite readily form emulsions of varnish in water; in general these are preferred agents. It is not necessary, however, in every case that an emulsifying agent be included; some varnishes apparently have ingredients present that function as emulsifying agents.

In the preparation of abrasive articles, varnish emulsions of the type described above are applied, for example by spreading rolls, upon a fibrous base, such as paper or cloth. The varnish component of the emulsion spreads out into a uniform film on the base, without substantially penetrating the base. When abrasive particles, such as sized sand grains, are spread upon the varnish film in accordance with the usual practice in the art, the particles are readily wet and surrounded by the varnish film, which upon hardening by air-drying or baking or the like, provides a tough, strong bond for the abrasive particles.

The term varnishes is used herein as equivalent to the expression "coating compositions. These compositions are generally solutions; but it is to be understood that oil-resin compositions in the liquid form not necessarily incorporating solvents and which can be applied in the same manner as varnishes to form coatings are comprehended within the meaning of the term varnishes.

I claim:

l. A method of making abrasive articles which comprises coating a fibrous base with an emulsion of a penetrative varnish composition in a volatile non-solvent, liquid, applying abrasive particles to the varnish film thereby produced, and hardening the varnish film.

2. A method of making abrasive articles which comprises coating a fibrous base with an emulsion of a penetrative varnish composition in water, applying abrasive particles to the varnish film thereby produced, and hardening the varnish film.

3. A method of making abrasive articles which comprises coating a fibrous base with an emulsion of a penetrative varnish composition including -a phenolic resin in a volatile non-rsolvent liquid,

applying abrasive particles to the varnish film thereby produced, and hardening the varnish film.

4. A method of making abrasive articles which comprises coating a fibrous base with an emulsion of a penetrative varnish composition including a phenolic resin of the oil-soluble type in a volatile non-solvent liquid, applying abrasive particles to the varnish film thereby produced, and hardening the varnish film.

5. A method of making abrasive articles which comprises coating a fibrous base with an emulsion of a penetrative varnish composition including a phenolic resin .01 the oil-soluble type in...water, applying abrasive particles to the varnish film thereby produced, and hardening the varnish film.

6. Method of making an abrasive article which comprises emulsifying a penetrative varnish composition in a non-solvent medium, coating a fibrous base with the emulsion, applying abrasive particles to the varnish film thereby produced, and hardening the varnish film.

7. Method of making an abrasive article which comprises emulsifying a penetrative varnish composition in water, coating a fibrous base with the emulsion, applying abrasive particles to the varnish film thereby produced, and hardening the varnish film.

8. Method of making an abrasive article which comprises emulsifying a penetrative varnish composition including an oil-soluble phenolic resin in water, coating a fibrous base with the emulsion, applying abrasive particles to the varnish film thereby produced, and hardening the varnish film.

9. Abrasive article cimprising a fibrous base, a binder consisting of a varnish composition inherently penetrative to said base forming a substantially non-penetrating uniform layer in direct contact with the surface of said base, and abrasive grains embedded in said varnish layer.

10. Abrasive article comprising a fibrous base, a binder consisting of an oil-resin varnish composition inherently penetrative to said base forming a substantially non-penetrating uniform layer in direct contact with the surface of said base, and abrasive grains embedded in said var nish layer.

13. Abrasive article comprising a paper base, a binder consisting of a varnish composition inherently penetrative to said base forming a substantially non-penetrating uniform layer in direct contact with the surface of said base, and abrasive grains embedded in said varnish layer.

14. Abrasive article comprising a fabric base, a binder consisting of a varnish composition inherently penetrative to said base forming a substantially non-peneratlng uniform layer in direct 10 contact with the surface of said base, and abrasive grains embedded in said varnish layer.

ROBERT P. COURTNEY. 

